During the growth in popularity of decorative emblems on garments such as T-shirts or jackets, there has been a continuing desire for ways to make such emblems retroreflective. On an outer garment worn at night, such retroreflective emblems would provide a bright return of light to oncoming motorists, thereby adding a safety feature, as well as increased decorative appeal, to the garments.
Insofar as known, no one has previously found a practical or commercially useful way to provide such retroreflective emblems. Some have proposed silk-screening a design onto a garment, and then while the design is still wet, cascading microspheres onto the design; but such an approach is messy, usually provides a nonuniform deposit of microspheres, and is impractical for obtaining high reflective brightness (which requires that the embedded surfaces of the microspheres be covered with a specularly reflective layer). Others have proposed mixing hemispherically specularly-coated glass microspheres into ink and printing such an ink onto the garment (see U.S. Pat. No. 3,535,019 (Longlet et al.)); but while such a product is useful for some purposes, it provides a reduced reflectance because the hemispherically-coated microspheres are randomly oriented within an applied coating. Still others long ago proposed the preparation of retroreflective decals comprising a layer of glass microspheres disposed over a printed design (see U.S. Pat. No. 2,422,256 (Phillippi)); but the suggested decal was a several-layer product which was likely stiff and unsuited for conformable garments.
In the past, the only commercial products suitable for retroreflective emblems or markings on garments have generally been single-colored tapes or sheet materials, with constructions as described in U.S. Pat. No. 2,567,233 (Palmquist et al.); U.S. Pat. No. 3,551,025 (Bingham et al.); U.S. Pat. No. 3,700,305 (Bingham); and U.S. Pat. No. 3,758,192 (Bingham). But none of these commercial products is useful to form the complex multi-colored designs that are in fashion and are needed to maximize the use of retroreflective emblems.
U.S. Pat. No. 4,102,562 (Harper et al.) and published International Application No. PCT/DK91/00325 (Publication No. WO 92/07990) disclose retroreflective transfer sheet materials comprising a carrier, a continuous monolayer of transparent microspheres partially embedded in the carrier, a specularly reflective layer (typically a transparent dielectric mirror) deposited onto the exposed surfaces of the microspheres, and a color layer printed over the microsphere layer in an imagewise pattern. In each reference, if the specularly reflective layer is a transparent dielectric mirror, the imagewise pattern or graphic design of the color layer is visible underneath the layer of microspheres in daylight. Although the daytime appearance of the resulting transferred emblem is similar to that obtained with heat transfers that carry no layer of microspheres (i.e., non-reflective transfers), when the emblem is illuminated in a dark room, the light retroreflected from the emblem optically masks the graphic design of the underlying color layer. In other words, only the color of the incident light is typically retroreflected from the emblem since the light is retroreflected directly from the dielectric mirror substantially without contacting the underlying graphic design.
The result is that, in spite of the above-described efforts, multi-colored designs or emblems on garments continue to be made non-retroreflective and the potential use of such emblems for safety purposes goes unrealized.